mtd: st_spi_fsm: Make of_device_id array const

Make of_device_id array const, because all OF functions
handle it as const.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/devices/st_spi_fsm.c

@@ -2058,7 +2058,7 @@ static int stfsm_remove(struct platform_device *pdev)
 	return mtd_device_unregister(&fsm->mtd);
 }
 
-static struct of_device_id stfsm_match[] = {
+static const struct of_device_id stfsm_match[] = {
 	{ .compatible = "st,spi-fsm", },
 	{},
 };